Adsorption, Abstraction, and Pairing of Atomic Hydrogen on Si(100)- (2×1)

Abstract

Using thermal desorption mass spectrometry, we have shown unambiguously that the adsorption of atomic hydrogen on Si(100)- $\left(2\times 1\right)$ leads to hydrogen pairing on silicon dimers at surface temperatures as low as 150 K and coverages as low as 0.2 monolayer. A detailed study of the adsorption kinetics shows a high probability of an abstraction reaction together with a coverage-dependent adsorption probability which is greater than expected for Langmuirian adsorption. These results, together with the known saturation coverage, are unified within the context of a “hot-precursor” mechanism for the adsorption of atomic hydrogen.